Surface treated layered lattice silicates and resultant products

ABSTRACT

A surface treated clay such as kaolin is prepared by a process in which the clay surface is preconditioned by treatment with gaseous hydrogen and then functionalized by reaction with a polymerizable organic moiety of an organic compound. The products are useful as fillers for rubber, resin, plastic, paper and the like.

RELATED APPLICATION

This application is a continuation-in-part of copending application Ser.No. 930,278, filed Nov. 12, 1986, now U.S. Pat. No. 4,784,495, which inturn is a continuation-in-part of U.S. patent application Ser. No.699,120, filed Feb. 8, 1985, now abandoned.

BACKGROUND OF INVENTION

This invention relates generally to siliceous minerals such asaluminosilicates and the like, and in particular relates to the productsof a method in which said mineral is pretreated to enhance subsequentfunctionalization, then is caused to react with a functionalgroup-containing variety of an organic compound.

The invention relates specifically to layered silicates of the typewhich can be represented by the general formula E_(i) M_(x) Si_(y) O_(n)(OH)_(m) where M is Al, Mg, or Fe, x=2 to 6; y=2 to 8, n=2 to 20, m=0 to8, and E_(i) is one or more exchangeable ions (K, Na, Mg, Ca, Ba, Fe,Li, etc.). These layered silicates will hereinafter in thisspecification be referred to as "layered lattice silicates".

In this disclosure, the term "functionalization" means using a reactantthat contains a functional group. The functional group subsists at leastto some extent in the product obtained except when an olefin is usedwhich leaves an alkane as product. The term "surface treated" means thatonly the surface is modified, that is, there is no intercalation in thelayered lattice silicate or breakdown of its structure.

In the instance of layered lattice silicates such as kaolin clays, ithas long been recognized that products having new properties and usescould be formulated by combining these aluminosilicates with organicmaterials. However, useful progress in this direction has tended to belimited by the lack of available covalent bonding at the mineral/organicinterface. In the past this difficulty has been partially overcome bysurface modification of the kaolinite through coupling of organosilanecompounds, and subsequent reaction between dependant silanes andorganics.

Thus, in Papalos U.S. Pat. No. 3,227,675, for example, kaolin clays aredescribed, the surfaces of which are modified with organofunctionalsilanes. A typical such agent, e.g., is a methacryloxypropyltrimethoxysilane. The kaolin clays so modified are advantageously used as fillersfor natural and synthetic rubbers and the like. It is also pointed outin this patent that such modified products can serve as intermediatesfor synthesis of new pigments, which are useful as fillers forpolylattice mers, elastomers and resins. This result obtains because thesilanes used to modify the kaolin clays are di- or polyfunctional, andonly one functional group, the silane, is attached to the clay, leavingthe remaining reactive groups to react further.

Additional references of this type include Iannicelli U.S. Pat. Nos.3,290,165, and 3,567,680.

However, the modification of aluminosilicates such as kaolin clays bythe use of organosilanes, is a complicated and expensive process. Amongother things, the cost of the organosilane itself is very high.Furthermore, the resulting products have only limited capability forfurther reaction, regardless of the particular organosilanes utilized.

It has heretofore been known in addition, that in certain instances hightemperature reactions of silicate films with hydrogen can be utilizedfor certain purposes, such as the production of hydroxide free silicafor optical glasses. It is also known to those skilled in the art thatproducts known as "hydrogen clays" can be produced by aqueous reactionof clays with mineral acids, as for example is described in U.S. Pat.No. 3,201,197. Such reactions have substantially no bearing upon thepresent invention, as will henceforth become evident.

In accordance with the foregoing, it may be regarded as as an object ofthe present invention, to provide a relatively simple and effectiveprocess for forming active intermediates from layered lattice silicates,such as aluminosilicates, which intermediates are eminently capable ofsubsequent functionalization with organic groups.

The kaolin group of clay represents a crystal structure wherein onegibbsite sheet is condensed with one silica sheet, forming a stablenon-expanding type crystal lattice, whereas the remaining two groups,the montmorillonite group and illite group, conform to the expandingcrystal lattice, consisting of a gibbsite sheet enclosed between twosilica sheets. Clays composed of the non-expanding lattice structuresare said to possess moderate surface activity and generally formrelatively free flowing systems in water; whereas those composed of theexpanding crystal lattice are capable of high colloidal activity andhydration, producing plastic and gel-like water systems.

It is therefore a specific object of the invention to combine kaolinclays with organic materials thereby rendering them lipophilic. That isto say, it is desirable to render normally hydrophilic layered latticesilicates such as kaolin, oleophilic, whereby they may be used asfillers for organic materials such as polymers, elastomers, resins andthe like.

SUMMARY OF INVENTION

Now in accordance with the present invention, the foregoing objects, andothers which will become apparent in the course of the ensuingspecification, are achieved in products yielded by a method comprisingpretreating layered lattice silicates in substantially dry particulateform, with a hydrogen-containing gas thereby activating the surfacethereof. By "activating the surface" is meant that the surface becomessusceptible to the surface bonding or reaction or polymerization oforganic moieties. The pre-treatment conditions the silicate in somemanner so as to make it more receptive to reaction with the functionalgroup-containing organic compound. At all events it has now been foundthat the final product according to the invention shows chemical bondingat the silicate surface.

The said pretreatment is conducted at temperatures above about 250° C.Typical temperatures utilized are in the range of from about 300° C. toabout 400° C.

The composition may be treated with gaseous hydrogen. This mixture mayinclude as well an inert gas carrier, such as nitrogen or argon.

The gaseous treating composition may further, and preferably does,comprise a mixture of hydrogen and nitrogen. The hydrogen may comprisefrom about 5% to 100% by volume of the total gas, with a preferred rangebeing from 5% to 50% by volume.

The contacting may be conducted in a fluidized bed reactor, with thegaseous components passing upwardly through a suitable diffuser plate,and into a fluidized bed of the particulate material being treated. Thecontacting may also be conducted in similar apparatus which providesgood gas-solids contact. Typical treatment times are from about 5 to 30minutes, depending upon concentration of the ingredients andtemperature, although longer times can be utilized.

Various layered lattice silicates, including minerals comprising thesame, may be treated by the method of the invention. Thus, for example,clays of the halloysite, illite, kaolinite, montmorillonite,palygorskite groups, and various other clays, can be readily treated bythe present invention.

The intermediates prepared by use of the present process are highlyreactive, and may lose their activity if substantial moisture oratmospheric oxygen are present. For this reason, once the saidintermediates are prepared, and until they are used, they must bemaintained in a substantially dry state.

The functionalization of the hydrogen treated silicate materials can beachieved by various methods, such as by contacting them under suitablereaction conditions with compounds having active organic groups, forexample, C═C. The reaction is suitably carried out with thefunctionalizing reactant in the fluid phase, i.e., in the liquid orpreferably the gaseous phase. This can be effected by varioustechniques, for example, in many instances by simple mixing of theintermediate with the reactant.

In general, since the pretreatment/reaction only involve the surface,times for these interactions are relatively short.

In general, the useful organic compounds contain polymerizable organicmoieties and include olefins, diolefins, acetylenes, allylic compoundsand vinyl compounds. These unsaturated compounds may, for example, behydrocarbon substituted or unsubstituted ethylene such as ethylene,propylene; hydrocarbon substituted or unsubstituted butadiene such asbutadiene, isoprene; vinyl pyridines, vinyl acetate, styrene, acrylicacid, phenyl acetylene, allyl mercaptans and allyl amines. Temperatureconditions are generally moderate, suitably above room temperature andup to about 300° C. Reaction times are short since one is onlysatisfying the surface demand, and a time in the range of about 15seconds to about 5 minutes will generally be sufficient although it maybe extended if desired up to about 1 hour.

The particulate products of the present invention are furthercharacterized in having particle size distributions (P.S.D.'s) whichsubstantially correspond to the unmodified particulate feeds which areused to produce same. Accordingly, the P.S.D. particulate product ispredetermined by selecting the input feed P.S.D. to meet the desiredP.S.D. in the end product.

No type of grinding or intense mechanical agitation is used, and thus asimple encapsulation ensues--there is no fragmentation of the originalparticles.

DETAILED DESCRIPTION

The invention will now be illustrated by a series of Examples, which,however, are to be considered as merely exemplary of practice of theinvention, and not as delimitive thereof.

EXAMPLE I Preparation of a Surface Modified Kaolin Clay

In this Example, the starting material was an air-floated kaolin clay,having approximately 60% by weight of the particles thereof less than 2microns equivalent spherical diameter (E.S.D.). A 400 gram sample ofthis material was initially dried for 11/2 hours in an oven attemperatures of about 150° C. The sample showed a weight loss,indicating that moisture had been successfully driven off from same, toproduce a substantially dry material.

The said sample was placed in a laboratory fluidized bed reactor, thesystem was equilibrated to 300° C., at which time a mixture of hydrogenand nitrogen in a volume ratio of 5 to 95 parts, at 300° C., was passedthrough the fluidized bed. The gas mixture was flowed at the rate ofabout 0.7 standard cubic feet per minute (SCFM), and served to sustainthe fluidized bed. The hydrogen treated clay was cooled to 80° C. in astream of nitrogen gas. 1,3 butadiene (at room temperature) was passedthrough the intermediate activated clay for one minute. The resultantsurface modified clay was found to be partially hydrophobic in a watersystem, in contrast to the properties of an untreated kaolin clay. Anelemental analysis showed an increase of 0.32% carbon. The clay wasfound to decolorize both a solution of potassium permanganate, and abromine in carbon tetrachloride solution, indicating the presence ofunsaturation on the clay. The carbon was not removed by either water oracetone washing. A differential scanning calorimetry measurement of thetreated clay showed that the organic was thermally stable on the claysurface to at least 300° C.

EXAMPLE II

In this Example, a further sample of an air-floated relatively finefraction of kaolin clay having a P.S.D. (particle size distribution)such that 60% by weight of the particles thereof were less than 2microns E.S.D., was subjected to hydrogen treatment in accordance withthe present invention. The sample was treated with a combination ofnitrogen and hydrogen under conditions generally identical to those ofExample I. The sample in particular, after being initially dried, wastreated in the laboratory fluidized bed reactor for a time of 15 minutesat a temperature of 280° C.

A portion of the resultant intermediate from this Example was maintainedunder argon and approximately 3 grams were transferred to a thick walledglass ampul (still under argon), with approximately 2% by weight ofallylchoride being added as a liquid at room temperature. The ampul wassealed and then placed in a 50° C. oven for 30 minutes. The resultantfunctionalized product was found to contain 0.15% allylchloride (basedon both carbon and chlorine analysis.) The resulting product did notdecolorize potassium permanganate solution or a bromine in CCl₄solution, indicating the disappearance of the unsaturated character ofthe allylchloride. Infrared spectra were obtained on the treated anduntreated clay samples. There was a definite appearance of a CH stretchin the 3050 to 2750 cm⁻¹ range for the treated clay sample. This organicwas not removed from the surface by acetone or water washing.

EXAMPLE III

In this instance, a 400 gram sample of an air classified kaolin wasinitially dried as with the procedure of Example I, and loaded into alaboratory fluidized bed reactor, and the temperature equilibrated at250° C. A fluidized bed was established by flow of nitrogen from asource having a regulated pressure of approximately 10 pounds per squareinch. 50% of hydrogen at 300° C. was flowed into the reactor with thenitrogen inert gas, and the treatment was carried out initially for 15minutes at 300° C. At the conclusion of the treatment, the intermediateproduct was cooled to 80° C. and allylmercaptan was vaporized in N₂ andflowed through the hydrogen activated clay for approximately 4 minutes(approximately 20 ml in total of allylmercaptan). There was a colorchange of the clay associated with the allylmercaptan treatment. Basedon an elemental analysis of total carbon, there was a 0.14% carbonincrease upon reaction, translating to approximately 0.29%allylmercaptan bonded to the surface.

EXAMPLE IV

In this instance, a 400 gram sample of an air classified kaolin wasinitially dried as with the procedure of Example I, and loaded into alaboratory fluidized bed reactor, and the temperature equilibrated at300° C. A fluidized bed was established by flow of nitrogen from asource having a regulated pressure of approximately 10 pounds per squareinch. 50% of hydrogen at 300° C. was flowed into the reactor with thenitrogen inert gas, and the reaction was carried out initially for 15minutes at 300° C. At the conclusion of the treatment, the sample wascooled to 70° C. and treated with propylene gas for 1 minute which wasjust passed through a heat exchanger at 300° C. The resultant clayshowed a total carbon content increase of 0.14%.

The products of the present invention are found to be particularlyuseful as fillers in polymers, elastomers, plastics, paints or papers.Where such materials, for example, are used as fillers in epoxycompounds, it is found that the resultant cured epoxy systems displayincreased hardness and higher shear adhesion strength than have beenobtainable with prior art fillers based upon kaolin clays, orsilane-modified kaolin clays.

The following Example V is representative of the improvements achievedin filled resin systems in accordance with the present invention.

EXAMPLE V

In this Example, three different surface modified kaolins were preparedby procedures similar to Example I, but with differing surface treatmentlevels as indicated below:

                  TABLE I                                                         ______________________________________                                        Sample    Treatment         % Carbon*                                         ______________________________________                                        A         H.sub.2 + 1, 3 butadiene (30 sec.)                                                              0.14                                              B         H.sub.2 + 1, 3 butadiene (2 min.)                                                               0.98                                              C         H.sub.2 + 1, 3 butadiene (1 min.)                                                               0.32                                              ______________________________________                                         *increase in total carbon content after reaction with 1, 3 butadiene     

The above products were then used as fillers in an otherwiseconventional EPDM (ethylene propylene diene monomer) insulationformulation. An untreated filler was also used as a control,specifically the untreated clay used in Example I. The insulationformulation was as follows:

                  TABLE II                                                        ______________________________________                                        EPDM Insulation Formulation                                                   Additive        parts per 100 parts EPDM rubber                               ______________________________________                                        Vistanlon* 4608 (EPDM)                                                                        100                                                           Zinc Oxide      5                                                             Stearic Acid    0.5                                                           Flectal H**     1.5                                                           Percardox.sup.+ 14/40 (peroxide)                                                              7.0                                                           Rhenufit.sup.++ Tac/s (coagent)                                                               2.0                                                           Filler (A, B, C or control)                                                                   150                                                           Sunpar.sup.+++ 2280 (oil)                                                                     30                                                            ______________________________________                                         *Esso Chemical                                                                **Monsanto (antioxidant)                                                      .sup.+ Akzo (curing agent)                                                    .sup.++ Bayer (initiating catalyst)                                           .sup.+++ Sun Oil Co. (lubricant)                                         

The above formulations were cured at 170° C. for 20 minutes and thephysical properties of the resultant samples were determined as follows:

                  TABLE III                                                       ______________________________________                                        PHYSICAL PROPERTIES OF EPDM FILLED                                            WITH VARIOUS KAOLIN SAMPLES                                                                            Mod-                                                         % Elon-  Ten-    ulus** Tear***                                               gation   sile*   100%   Newtons Shore A                               Filler  at Break (MPa)   (MPa)  per mm  Hardness                              ______________________________________                                        A       440      6.6     3.5    54      68                                    B       800      8.0     2.4    68      67                                    C       800      6.5     2.4    51      67                                    Untreated                                                                             340      4.2     2.5    55      67                                    kaolin                                                                        (control)                                                                     ______________________________________                                         *Tensile is the force per unit area required to stretch the test piece to     its breaking point.                                                           **Modulus at 100% is the stress required to stretch a test piece of rubbe     to 100% elongation and is repeated in units of mega Pascals.                  ***Tear strength is the force required to tear a unit thickness of a test     piece.                                                                   

As seen in Table III, the EPDM samples filled with the products of theinvention show very marked improvements in elongation and tensile, ascompared with the samples filled with the prior art untreated kaolins.

EXAMPLE VI

In this Example a further surface modified kaolin was prepared as inExample IV and was then used as a filler at the 30% weight level in apolypropylene system. Physical properties were evaluated for theresultant filled system and compared with such properties for anunfilled polypropylene and for a polypropylene filed (at 30%) with anuntreated kaolin clay. Results are set forth in Table IV below:

                  TABLE IV                                                        ______________________________________                                        PHYSICAL PROPERTIES OF                                                        FILLED POLYPROPYLENE                                                                   Tensile                                                                       Modulus Tensile Strength                                                                           % Elongation                                             (MPa)   (MPa)        at Break                                        ______________________________________                                        Polypropylene                                                                            1440      25.3         8                                           (PROFAX) filled                                                               with untreated                                                                kaolin control                                                                Unfilled poly-                                                                           1220      31.8         15                                          propylene control                                                             Polypropylene                                                                            1775      33           6                                           (PROFAX) filled                                                               with treated                                                                  kaolin                                                                        ______________________________________                                    

It will be seen from Table IV that the polypropylene system filled withthe treated clay displayed an increase in tensile modulus and tensilestrength over either of the control formulations.

EXAMPLE VII

An air-classified kaolin (80% less than 2 micrometers, E.S.D.; surfacearea=19 m² /g) was treated in a fluidized bed reactor at 180° C. for 30minutes in a 50%/50% by volume hydrogen/nitrogen atmosphere. It wascooled to room temperature in a 100% N₂ atmosphere. A sample wastransferred to a glass ampul and 2 weight % 2-vinylpyridine (a liquid)based on the weight of the clay was introduced into the ampulatmosphere. The ampul was flushed with nitrogen to remove any traces ofoxygen and sealed. It was placed in an oven at 170° C. and reacted for30 minutes. At the end of the 30 minutes reaction time, the ampul wasremoved from the oven and cooled to room temperature. The ampul wasopened, the clay removed and split into 2 samples. One sample was waterwashed. The other was acetone/ether washed. The resulting washedproducts contained 0.82% 2-vinylpyridine as determined by carbon andnitrogen analysis.

EXAMPLE VIII

An air-classified kaolin clay as described in Example VII was treated ina fluidized bed reactor in 50%/50% by volume N₂ /H₂ atmosphere for 5minutes at 305° C. The clay was cooled in N₂ to 178° C. and acetylenegas was then passed through the clay for 5 minutes. The clay was furthercooled to room temperature in a N₂ atmosphere. The treated sample wasanalyzed by carbon species. The resulting clay has a carbon content0.16% greater than before the reaction. None of the organic was removedby solvent washing.

EXAMPLE IX

The same kaolin as in Example VII was treated in a fluidized bed at 300°C. for 5 minutes in a 50%/50% by volume N₂ /H₂ atmosphere. The kaolinwas cooled to room temperature in N₂. 100 g of the H₂ treated kaolin wastransferred under N₂ to a Waring Blendor and treated with 0.25 weight %allylamine for 5 minutes. The resulting treated kaolin were analyzed forcarbon and nitrogen before and after washing with acetone. The treatedkaolin had a carbon content of 0.11% carbon and 0.026% nitrogen afterreaction. The N and C content did not change upon solvent washing.

EXAMPLE X

An air-classified kaolin (82% less than 2 micrometers E.S.D.; surfacearea=20.2 m² /g) was treated in 50%/50% by volume N₂ /H₂ atmosphere at300° C. for five minutes. The resulting kaolin was cooled to roomtemperature in a nitrogen atmosphere. 100 g was transferred undernitrogen to a nitrogen filled Waring Blendor and treated with 0.5%ethylmercaptan. The system was allowed to react at room temperature forfive minutes. The resulting kaolin showed an increase in carbon andsulfur content of 0.29 and 0.29% respectively. The content of carbon andsulfur was unchanged by acetone or water washing.

EXAMPLE XI

An air-classified kaolin (82% less than 2 micrometers E.S.D.; 20.2 m² /gsurface area) was treated in a fluidized bed reactor in a 50%/50% N₂ /H₂atmosphere at 312° C. for fifty minutes. The kaolin was cooled in astream of nitrogen to 40° C. and then reacted for 10 minutes with allylamine which was vaporized in a stream of argon. At the end of thereaction, the sample was analyzed for carbon and nitrogen by elementalanalysis, indicating 0.42% allylamine had reacted with the surface. Noneof the organic was removed by solvent washing.

While the present invention has been particularly set forth in terms ofspecific embodiments thereof, it will be understood in view of theinstant disclosure, that numerous variations upon the invention are nowenabled to those skilled in the art, which variations yet reside withinthe scope of the present teaching. Accordingly, the invention is to bebroadly construed, and limited only by the scope and spirit of theclaims now appended hereto.

What is claimed is:
 1. A surface-treated layered lattice silicateproduct which comprises a particulate layered lattice silicate, theparticle surfaces of which have been preconditioned by treatment withgaseous hydrogen to provide moisture-free catalytic sites and thenfunctionalized by reaction, wherein direct binding to the treatedsurfaces takes place, with a polymerizable organic moiety of an organiccompound.
 2. A product in accordance with claim 1, wherein saidcomposition comprises an aluminosilicate.
 3. A product in accordancewith claim 2, wherein said aluminosilicate is a kaolin clay.
 4. Aproduct in accordance with claim 1, wherein said particulate has apredetermined particle size distribution which substantially correspondsto the particle size distribution of the surface-unmodified layeredlattice silicate from which the product particulate is produced.
 5. Acomposition of matter for use as a filler in paper, rubber, resin andplastic systems comprising: a particulate kaolin clay, the surface ofwhich has been activated by treatment with gaseous hydrogen to providemoisture-free catalytic sites, and the resultant surface-activatedproduct functionallized by reaction, wherein direct binding to thetreated surface takes place, with a polymerizable organic moiety of anorganic compound.
 6. A filled resin system, comprising a resin matrixbinder; and as a filler; a dispersed particulate kaolin clay, thesurface of which has been activated with gaseous hydrogen to providemoisture-free catalytic sites, and the resulting surface-activatedproduct functionallized by reaction, wherein direct binding to thetreated surface takes place, with a polymerizable organic moiety of anorganic compound.
 7. A filled system in accordance with claim 6, whereinsaid matrix binder is a cured EPDM.
 8. A filled system in accordancewith claim 6, wherein said matrix binder is a polypropylene.